From flickering fireflies in Northeastern backyards to bizarre fishes illuminating the deep ocean’s perpetual dark, the tree of life is spangled with organisms that blink, glow, flash, and glitter. How do organisms use bioluminescence, and how do scientists study it? Rare in land animals, the ability to produce light is much more widespread in marine life. A new generation of custom-designed equipment is enabling scientists to observe and collect creatures rarely seen alive before. In the deep ocean off the Solomon Islands, for example, Museum biologists found animals communicating with light. Many more intriguing discoveries await as we explore Earth’s final frontier, the deep sea.